Cameras are one of the major applications of image sensors. A camera is essentially consisted of an image sensor and a proper lens. Focusing of a conventional camera lens is typically associated with the problem of non-uniformity in imaging characteristic between a central area and a peripheral area of the lens. As a result, an image captured by such a lens generally has a lower quality in its peripheral area than in its central area in terms of, e.g., clarity and brightness. This phenomenon depends on the nature of the lens and is thus hard to be improved through lens modifications.
In order to solve the above-described non-uniform imaging quality problem, Sony Corporation has proposed the use of an arc-shaped silicon substrate for image sensor chip. This arc-shaped configuration imitates the principles of physics in optical imaging of the human eye, in which the lens is equidistant from each photodiode in the image sensor, thereby allowing comparable imaging qualities of peripheral and central areas of the lens. Although this is theoretically capable of solving the non-uniform imaging problem of the conventional devices, formation of the arc-shaped silicon substrate can introduce additional stress to the chip, which has the following two possible consequences: 1) cracking of the chip; and 2) a certain degree of deterioration of imaging quality, particularly in terms of, for example, dark current, white pixel and noise. Avoidance of these risks may impose extremely strict requirements on the production process and thus lead to a significant reduction in the yield.
Therefore, how to mitigate the aforementioned drawbacks of the conventional cameras is one of the major issues to be addressed by those skilled in the art.